Six people were injured in the incident after takeoff from Philadelphia International Airport on Sunday afternoon, US Airways said.

Five people, including two flight attendants, were taken to hospitals for treatment after the plane returned to Philadelphia, said spokesman Bill McGlashen. The sixth didn’t need hospitalization.

Pensiero told CNN he was surprised to hear that anyone was injured. “I don’t know who would have had their seat belt off,” he said. “We were not in smooth air at any time.”

Other passengers he spoke with described a woman hitting the top of the aircraft, her feet up at their eye level, Pensiero said.

Soon after the incident, the crew asked any medical personnel on board to hit their call lights, Pensiero said.

There had been some reports of light turbulence in the area, but nothing as severe as what the plane ran into.

The Federal Aviation Administration will investigate.

In a separate incident, the wing of a WestJet 737 clipped the horizontal stabilizer of a JetBlue plane while on the ground at Orlando International Airport. The horizontal stabilizer is a lifting surface on a plane’s tail.

The WestJet flight was pushing back from the gate when the incident happened, according to the FAA.